Rheostat.



N0. 7|6,222. Patented DBO. l5, |902.

' J. L. HALL.

RHEOSTAT. (Application med .rune 27, 190'1.,

(No Model.)

'1 IMI I1 .lohn L Hall.

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Winesses.

' switch-arm or` brush adapted to sweep over a UNITED STATES APATENT OFFICE,

JOHN L. HALL, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A` CORPORATIONVOF NEW YORK.

RH EO STAT.

SPECIFICATION forming part of Letters Patent N O. I716,222, dated December 16, 1902.

l l Application filed June 27, 1901. Serial No. 66,207. (No model.)

To a/ZZ whom it may concern.-

Be it known that I, JOHN L. HALL, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvementsin Rheostats, (Case No. 2,05l,) of which the following is a specification.

This invention relates to controlling-rheostats of that type in which the translating device governed or controlled by the rheostat is automatically cut out of circuit in case of failure of the supply-current. Such devices are largely employed in connection with electric motors, in which current in starting the motor must be turned on gradually, the rheostat-switch being arranged to cooperate with the control-magnet, so that in case of failure of current the' magnet is discharged and the switch-arm shifted to an open-circuit position, thereby cutting out the motor and leaving it in proper condition for restarting when current is again put on the circuit. It is desirable in such systems to permit the rheostat to be maintained at intermediate resistance positions, so as to graduate the power or speed of the motor, and my invention is designed to accomplish this result. To that end I provide a spring controlled plurality of contacts connecting with intermediate points of a resistance in circuit with the translating device, and I provide a swinging frame adapted to latch or. retain the arm in a plurality of different positions, from any one of which it may be automatically released in case of failure of the supply-current. The latching-frame is a pivoted structure carrying an armature cooperating with an electromagnet in the circuit which is held by the magnet when the circuit is closed and held in that position so long as current iiows. On a predetermined decline of 'current or in case of failure of current the frame is retracted by a control-spring, thereby releasing the spring-actuated switch and permitting the rheostat to automatically open the circuit.

My invention therefore comprises a rheostat having a retractile switch-arm and a movable frame carrying a retaining armature controlled by a magnet in the circuit, said frame being provided with a plurality of stops and adapted to lock the brush at one or more intermediate resistance positions.

Other features of novelty will be more particularly hereinafter described, and will be definitely indicated in the claims appended to this specification.

In the accompanying drawings, which illustrate -the invention, Figure l is a side elevation of a rheostat embodying my improve# ments, and Fig. 2 is a plan view of the same.

l represents a base, of any suitable material, preferably some reproof insulating material, such as slate, on the under side of which may be arranged in the usual manner resistance cards or sections connectingwith a v plurality of contact-points 2 2, the., and 3 3, tc. These may be arranged with reference to the resistance units and the external circuit in any desired way, according to the use to which the rheostat is to be put. As such arrangements are commonly employed and well understood, I deem it unnecessary to describe them in detail. It will be understood by those familiar with the art that when a metallic switch-lever L1, operated bya handle 5 and centrally pivoted, as at 6, is swung over the range of contacts the circuit,with the trans lating device to be controlled, will be closed and its resistance gradually cut out as brushes carried by the outer ends 7 7a of the switchlever are moved over the contacts. The end of the lever carries a spring-pin 8, adapted to be detained in any one of a plurality of notches 9 on a swinging frame lO, controlled by a retractin g-sprin g 1l. This frame is pivotally connected with the armature 12 and is always within the grasp of the field of force of a control-magnet 13 in circuit with the rheostat. The final contact before breaking, as 3, may be provided with an arc-rupturing device, such as a blow-out magnet 1l, the extended pole-piece l5 of which may be extended so as to form a magnetic field abouty the contact. The frame l0 may be conveniently given an arc shape, so that the notches 9 will always be in cooperative relation to the springpin S. Any desired number of notches may be provided in positions corresponding to the several contacts, so that ,the arm will be latched in contact relation. I preferably provide these notches to correspond with the up- IOO per contacts of the range, so that the motor or other translating device will be held in a definite position with a considerable portion of the resistance cut out.

In operation when the lever 4 is turned by the handle 5 the circuit is first closed by engagement of the first pair of contacts, and resistance is then gradually cut out, the magnet 13 being energized and its armature 12 attracted, thereby locking the frame against an opening movement and permitting the spring-pin 8 to engage the notches 9 when the control-lever is shifted part way. If at this point the arm be released, the tension on the spring 8 will be sufficient to frictionally lock it with the frame 10, thereby holding the motor or other translating device under a moderate current. l Ifa greater strength of current is desired,the arm may be shifted to a higher notch. If while in this position of adjustment current should fail,the magnet 13 will be denergized, permitting the spring 16 to retract the frame 10, and thus release the spring-controlled arm 4.-. In case the full power of the current be desired the arm may be shifted to the extreme notch. Thus the safety of the motor or other translating device is guaranteed for any position of adjustment, since the circuit will automatically be opened on failure of current. Such provision is particularly necessary in case of electric motors in order to prevent the motor being left in circuit with a small amount of resistance in series with its armature in case of failure of current and subsequent turning on of current.

The tension on the spring-pin 8 and the slope of the notches in the frame l0 are so designed that the operator may push the arm 4 past the notches; but the engagement is sufficiently firm to hold the arm set against the tension of the retractingspring 16. The strength of spring 16 is of course sufficient to overcome that of spring ll.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent of the United States, is-

1. A rheostat provided with a retractile switch, a retaining-magnet to lock the switch in intermediate positions of resistance adjustment, a movable frame controlled by the magnet provided with a plurality of stops to latch the switch-arm at the several intermediate positions, said frame adapted to shift when the magnet weakens to a predetermined degree to release the switch-arm.

2. A rheostat provided with a retractile switch-arm, a spring-actuated detent on said arm, a frame coperating with said detent pivoted to yield in the direction of strain on the arm and adapted to engage the switch in different positions, and electromagnetic means for releasing the engagement.

3. A rheostat provided with a spring-actuated switch-arm, a pivoted frame provided with a plurality of notches to arrest said arm at intermediate positions of resistance adjustment,said frame being pivoted to swing in the direction of strain on the switch-arm in releasing, an armature carried by said frame, and a magnet to retain said armature during a iiow of current of predetermined strength.

4. A rheostat provided with a spring-actuated sWitch-arm,a detent carried by said arm, a swinging frame adapted to engage said detent, said frame being mounted to yield in the direction of rotation of the arm and outwardly therefrom to free the detent, an armature for retaining said frame in latching position, and a magnet for releasing the armature upon decrease of current below a predetermined point.

5. A rheostat provided with a spring-actuated switch, a detent carried thereby, a frame coperating with said detent, links supporting the same for movement in the direction of the switch-arm, and an electromagnet for holding said frame rigid during a flow of current.

In witness whereof I have hereunto set my hand this 24th day of June, 1901.

JOHN L. HALL.

Witnesses:

BENJAMIN B. HULL, MARGARET E. WooLLnY. 

